Group III-nitride and its ternary and quaternary compounds are prime candidates for fabrication of visible and ultraviolet high-power and high-performance optoelectronic devices and electronic devices. These devices are typically grown epitaxially as thin films by growth techniques including molecular beam epitaxy (MBE), metalorganic chemical vapor deposition (MOCVD), or hydride vapor phase epitaxy (HVPE).
In conventional MOCVD, the precursors (such tri-methyl gallium, ammonia etc.) are supplied continuously to the reactant chamber. Growing III-nitride and other semiconductors requires a very high growth temperature (e.g., about 1000° C. to about 1100° C.). Even higher temperatures are required for growth utilizing relatively large percentages of certain materials, such as those including Group III elements such as Al, B or Ga, and/or Group V elements such as As, N, P, and Sb, such as at growth temperatures of about 1300° C. to about 1450° C. At these extremely high temperatures, however, the precursors tend to combine in the chamber and “rain down” onto the surface of the substrate, effectively forming adduct particles thereon. These adduct formations during MOCVD hamper the subsequent epilayer growths by increasing the number of stacking faults as well as the dislocation density.
A pulsed metal organic chemical vapor deposition (P-MOCVD) or pulsed atomic layer epitaxy (PALE), in which the precursors are supplied with alternative supply of sources, alleviates the above mentioned problem. This alternative or pulsing technique not only suppress the adduct formation but also provides a unique opportunity to bend the dislocation propagation, to deposit monolayers of material thereby decreasing the slip (which is often the reason for stacking fault generation). Thus, P-MOCVD makes an attractive technique for substrate and epilayer growth and device fabrication.
Although the P-MOCVD alleviates some of the potential problems plaguing III-nitride devices (especially over non-polar substrates and materials) and represents an enabling technology for the growth of non-polar III-nitride devices, the relatively high defect density in the directly-grown non-polar or semi-polar III-nitride films reduces the efficiency of subsequently grown devices compared to what could be achieved by homoepitaxial growth on a perfect substrate.
Thus, a need exists for a more efficient system for MOCVD growth of group III, group V, group III-V, or any other type of semiconductor material, where higher temperatures and pulsing can be utilized but with a decrease in defect density on the formed films.